ENERGY GUEST BLOG -- WILLIAM M. BOWEN OF CLEVELAND STATE UNIVERSITY

Windmill at Progressive Field is much more than window dressing

Blog Entry: October 02, 2012 4:30 AM | Author: WILLIAM M. BOWEN

William M. Bowen is professor of public administration and urban studies at the Maxine Goodman Levin College of Urban Affairs at Cleveland State University. He's also associate editor of the International Journal of Energy Technology and Policy.

Lots of people have seen Prof. Majid Rashidi's windmill at Progressive Field, but far fewer understand it and some of the energy policy issues it brings up.

The windmill is based upon recognition of the dependency of wind power on wind velocity. Mechanical power contained in a stream of wind, and subsequently captured by a typical horizontal axis turbine, is mathematically proportional to the velocity of the wind raised to the third power. Therefore, if the wind speed increases by a factor of 2, for example, the wind power increases by a factor of 8 — 2 raised to the power 3 is equal to 8.

So if one day the wind speed is 10 miles per hours, and on another day the wind speed becomes 20 miles per hour, the power generated by any given wind turbine during the second day will be 8 times higher than that of the first day.

The role of the helical structure in Prof. Rashidi's windmill is to increase the natural wind speed before it reaches the turbines. The structure deflects the wind and increases the wind speed by a factor of about 1.65. This, in turn, results in an increase of power imparted to the wind turbines by a factor of 1.65 x 1.65 x 1.65 = 4.49.

This has an intuitive explanation, too. If, for a moment, we imagine that the wind deflecting structure is removed from the system, some of the stream lines of the wind flow will never reach the turbines but rather will simply pass through the two columns of the turbines installed in the grooves defined by the helical structure; therefore, all the energy potential in that wind will not be captured.

Prof. Rashidi's windmill has some serious advantages beyond simple potential for displacing new bulk power generation.

One advantage is cost. Each turbine currently costs about $10,000. On the basis of the principles I've just explained, the four turbines on Progressive Field produce the same amount of power as would 16 equivalently-sized, standalone turbines. Simple math dictates that even if the helical structure were to cost $60,000, the cost of Prof. Rashidi's windmill would still be $90,000 less than standalone turbines that would produce an equivalent amount of power.

(For those of you who like to do the math, it would be $160,000 for 16 turbines at $10,000 each, or $100,000 for a Rashidi system with one $60,000 helical structure feeding four, $10,000 turbines.)

'Seriously cool'

Another advantage is that it enables wind turbines to be set up in cramped settings found in urban areas. It is not possible to set up large wind turbines like the one at Case Western Reserve University in most urban settings.

But the seriously cool advantage is that Prof. Rashidi's windmill makes wind power far more viable in low-wind places such as Cleveland. Wind turbines need minimum wind speeds, below which they are basically useless. Unfortunately, in Cleveland we have a lot of days when the wind never reaches those minimum speeds.

But by effectively increasing the wind speed, Prof. Rashidi's windmill significantly reduces the number of such days, making wind power a much more viable option. It is a lot like bringing some of the energy potential found in Texas to Cleveland. This has nothing to do with either cost or increasing efficiency, but rather with making wind turbine useful in low wind-speed areas.

While Prof. Rashidi's innovation is interesting and valuable in its own right, it also exemplifies a policy issue I plan to explore in my future blog entries.

Innovation is necessary for economic growth and development, but so is the adoption and diffusion of innovation. What are the social and institutional impediments to the diffusion of not only this windmill, but similar energy innovations throughout the country? We'll explore those in another blog soon.

William M. Bowen is professor of public administration and urban studies at the Maxine Goodman Levin College of Urban Affairs at Cleveland State University. He's also associate editor of the International Journal of Energy Technology and Policy.

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